I. A. Strelina

Conformational and dynamo-optical properties of fluorinated poly(p-phenylene-1,3,4-oxadiazole-imide-amide) molecules in solutions

Abstract Conformational parameters of the fluorinated poly( p -phenylene-1,3,4-oxadiazole-imide-amide) molecules in dilute solutions in N , N ′-dimethylacetamide, N , N ′-dimethylformamide and 96% sulphuric acid were evaluated by using the data of hydrodynamic and dynamo-optical investigations. Optical anisotropy of the statistical Kuhn segment was found to be about half of that for poly(amide-benzimidazole) and close to that previously obtained for poly( p -phenylene-1,3,4-oxadiazole) molecules. The observed effect is referred to the higher equilibrium flexibility of the polymer chain attributed to the hexafluoroisopropylidene units incorporated into the molecule backbone. Noticeable degradation of the polymer molecules in solution in 96% H 2 SO 4 at ambient temperature was detected and characterised.

Synthesis, hydrodynamic, and conformational properties of poly(N-acryloyl-11-aminoundecanoic acid) in solutions

Poly(N-acryloyl-11-aminoundecanoic acid) samples are synthesized in monomer solutions occurring in both micellar and nonmicellar states. It is shown that polymeric ionogenic surfactants of various molecular masses can be prepared through variation in the concentration of a polymerizable surfactant or in the ionic strength of a solution. The polymer of interest is investigated in detail via the methods of molecular hydrodynamics (viscometry, isothermal diffusion, and velocity sedimentation), dynamic light scattering, GPC, and scanning probe microscopy. The solubility of the polymer in various solvents is examined in detail, and the tendency of this polymer toward association in DMF solutions is discovered. The equilibrium rigidity of macromolecules, which is characterized by the Kuhn segment length A = 100 × 10−8 cm, and the effective hydrodynamic radius are determined in a dioxane-cyclohexanol mixed solvent.

Optical, dynamic, and electro-optical properties of poly(N-acryloyl-11-aminoundecanoic acid) in solutions

The optical, electro-optical, and dynamic characteristics of poly(N-acryloyl-11-aminoundecanoic acid) in organic solvents and of the sodium salt of its monomer in water were studied via the methods of flow birefringence, equilibrium and nonequilibrium electric birefringence, and dynamic light scattering. It is shown that, in aqueous solutions, the monomer forms coarse particles of both symmetric and asymmetric shapes. The linear dimensions of these particles are estimated from the data of translational and rotational diffusion. Polymer macromolecules in organic solvents feature negative anisotropy of optical polarizability. Contributions of optical microform and macroform effects to the observed flow birefringence are analyzed in detail. The intrinsic optical anisotropy of the monomer unit of the polymer, which correlates well with the corresponding values for comb-shaped polymers of a similar structure, is estimated. It is shown that polymer molecules lack marked intrinsic permanent macromolecular dipoles and that electric birefringence in their solutions is associated with macroscopic induced dipole moments that appear during orientation of the dipole moments of polar groups in side chains of the polymer under application of an electric field.

Hydrodynamic and dynamo-optical properties of poly(1,3-phenylene-1,3,4-oxadiazole) molecules in sulphuric acid

Abstract Translational diffusion of the macromolecules, intrinsic viscosity and flow birefringence induced in dilute solutions of poly(1,3-phenylene-1,3,4-oxadiazole) (PMOD) in conc. sulphuric acid has been investigated. Molecular-weight dependences of hydrodynamic and dynamo-optical properties are established over the M range from 8.1×103 to 87×103. Experimental data agree well with the theories developed for translational friction and intrinsic viscosity of the wormlike chains with the following molecular parameters: mass per chain unit ML=22.7 Dalton/A, the Kuhn segment length A=59±4 A, the chain diameter d=4±1.5 A. Hindrance to intramolecular rotation is characterized by the parameter σ=1.7. The shear optical coefficient was found to be approximately 1.7 times lower the value of that obtained in the same solvent for the para-phenylene isomer of this polymer, being in good agreement with higher equilibrium flexibility of the PMOD molecule chains in solutions as determined herein from the hydrodynamic data.

Structure and properties of macromolecules with side dendrons based on L-aspartic acid

The molecular characteristics of cylindrical first-third generation dendrimers carrying dendrons based on L-aspartic acid are compared. It is shown that both the generation number of side dendrons and their structure determine the conformational, hydrodynamic, optical, and dipole characteristics of dendrite macromolecules. It is found that the studied class of cylindrical dendrimers is distinguished by a marked amount of intramolecular hydrogen bonds between side dendrite substituents. These bonds ensure the unusual combination of high kinetic rigidity and a compact conformation (low equilibrium rigidity) of macromolecules. The rupture of hydrogen bonds leads to an enlargement of molecular coils (an increase in equilibrium rigidity) that is accompanied by a sharp drop in kinetic rigidity.

Chitosan and its derivatives in extensional and shear flows

Allylchitosan and propylchitosan with different degrees of substitution were prepared on the basis of chitosan from shrimp chitin. The dynamics of semidilute electrolytic polymer solutions of chitosan derivatives in acetic acid was studied by measuring birefringence in extensional and shear flows and by means of viscometry. The optical shear coefficient and critical velocity gradients corresponding to the loss of stability of the macromolecular coil in extensional flow were found. The chain relaxation times depending on the polyelectrolyte concentration and ionic strength of solution were determined.

Flow birefringence and optical anisotropy of molecules of copolymers of para- and meta-phenylene-1,3,4-oxadiazoles

Abstract Flow birefringence (Maxwell effect) and orientation of macromolecules were investigated in a flow of sulphuric acid solutions of some copolymers of meta- and para- aromatic 1,3,4-oxadiazoles differing in the molar content of the components. According to hydrodynamic data, the molecular weights of samples of copolymers and the corresponding homopolymers range from M=25×10 3 to 33×10 3 . This corresponds to the number of segments in the chain from 19 to 21. Comparison of dynamo-optical data with the corresponding properties of homopolymers has shown that the dependence of flow birefringence on the molar composition of the copolymer obeys the additivity law of chain flexibilities.

Dynamo-optical properties of poly(naphthylene oxadiazole)s in sulphuric acid

Abstract Flow birefringence induced in dilute solutions of poly[(1,4-naphthylene)-2,5-diyl-1,3,4-oxadiazole] and poly[2,6-naphthylene)-2,5-diyl-1,3,4-oxadiazole] in conc, sulphuric acid has been investigated. The shear optical coefficient was found for these polymers to be approximately double the value of that obtained in the same solvent for poly[(para-phenylene)-2,5-diyl-1,3,4-oxadiazole]. Rigid-chain behaviour of the polymers was characterized by hydrodynamic and dynamo-optical parameters evaluated with application of the worm-like chain model and the “method of similar structures”. Change in optical anisotropy of a chain unit induced by incorporation of naphthylene groups into the main chain has been evaluated.

Hydrodynamic, optical, and electrooptical properties of macromolecules of third-generation cylindrical dendrimers in chloroform and dichloroacetic acid

Acrylic polymers containing side dendrons of the third generation based on L-aspartic acid have been studied via the methods of molecular hydrodynamics, dynamic and static light-scattering, optics, and electrooptics. There are marked differences in hydrodynamic and optical properties of the macromolecules under study and previously examined polymers with side dendrons of first and second generations. In the range of degrees of polymerization from 10 to 40, these macromolecules possess an extremely low shape asymmetry. Experiments demonstrate the predominant orientation of end side dendrons along the main molecular chain. In chloroform solutions, the orientation of macromolecules in hydrodynamic and electric fields occurs according to the large-scale mechanism. In dichloroacetic acid, the hydrodynamic dimensions of macromolecules decrease, an effect that is accompanied by an increase in the kinetic flexibility of polymer chains.

Synthesis and study of poly(N,N,N,N-trimethylmethacryloyloxyethylammonium) methyl sulfate in longitudinal and shear flows

Samples of poly(N,N,N,N-trimethylmethacryloyloxyethylammonium) methyl sulfate prepared by suspension and bulk polymerization were studied.